Transportable pontoon

ABSTRACT

A foldable, multi-hull pontoon suitable for use in bridging or as a ferry, has a sequence of trapezoidal hull plates (1) successively hinged to one another at their parallel edges so as to fold in concertina fashion, alternate pairs of the plates being mutually and transversely webbed at each end with collapsible triangular bulkheads (7) which define with the hull plates a series of triangular section hulls (13). Gunwale spacing beams (40) are provided to stabilise the opened pontoon and to provide trackways.

TECHNICAL FIELD

This invention relates to a pontoon which can be folded fortransportation upon a road vehicle. The pontoon is particularly, but notexclusively, applicable for use in bridging or as a ferry.

BACKGROUND ART

The majority of known transportable pontoons have the disadvantage ofbeing bulky and are disproportionately expensive to transport, a verylarge part of the transported volume being air. Attempts have been madeto improve this situation by designing nestable pontoons, but even withthese, a considerable amount of air space still requires transporting.Furthermore, most existing pontoons must be launched and assembledindividually and their deployment can be a time-consuming task in anybridging or ferrying operation.

The present invention seeks to provide a foldable pontoon suitable forrapid deployment and having minimal enclosed air space in the transportmode.

DISCLOSURE OF INVENTION

According to the present invention a transportable pontoon includes: amultiplicity of substantially planar hull members each having a keeledge and a parallel gunwale edge, which members are successively hingedin sealed relationship at alternately conjoined keel edges and gunwaleedges so as to fold respectively inwardly and outwardly in concertinafashion; and a collapsible bulkhead member extending in sealedrelationship between each inwardly folding pair of hull members adjacenteach end thereof, which bulkhead members define with the hull members asequence of parallel hulls when the pontoon is extended.

The bulkhead members may each conveniently comprise a flexible membranewhich will fold between the hull members when they are closed towardsone another. Alternatively each bulkhead member may comprise a centrallyarticulated pair of plates, hinged at their outer edges to theassociated hull members so as to fold inwards when the pontoon isfolded.

Sealed hinged inter-connection of the hull and bulkhead members may beconveniently achieved by the use of flexible joints sealed between therespective members. Alternatively, where a more robust construction isrequired, the hinges are preferably of conventional, non-sealing pintype in combination with a supplementary sealing means, for example, aflexible membrane sealed to the conjoined members in parallel with thepin hinge so as to bridge the gap between the members.

The hull members are preferably of a buoyant material and weighted atthe keel edges so as to have position meta-centers to ensure that thepontoon will float upright when folded. This permits the pontoon to bespeedily launched whilst still folded and easily unfolded whilstwater-borne thus avoiding the necessity of employing cranes.

The pontoon preferably further includes at least one gunwale spacingbeam for use when the pontoon is opened, which beam is provided withspaced engagement means successively co-operative with each conjoinedpair of gunwale edges so as to locate them. The beam also providestransverse stiffening to the hulls.

The spacing beam may also be used to connect together two similarpontoons by co-engaging the outer-most gunwales of both, thereby toextend the sequence of parallel hulls. These spacing beams mayadditionally be arranged to serve as trackways or to support subsidiarytrackways.

BRIEF DESCRIPTION OF DRAWINGS

An embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawings of which

FIGS. 1 and 2 are a plan view and an end elevation view respectively ofan unfolded, 6-hull pontoon,

FIG. 3 is a view of the same pontoon folded for transportation, and

FIG. 4 is a representation of the same pontoon during launch.

BEST MODE FOR CARRYING OUT THE INVENTION

The six-hull pontoon illustrated in FIGS. 1 and 2 comprises twelveidentical trapezoidal hull plates 1 of a bouyant composite material suchas a resin honeycomb within an alloy skin, each plate having a keel edge2, a gunwale edge 3 and two bulkhead edges 4. The plates 1 aresuccessively interconnected by inner hinges 5 at the keel edges 3, andouter hinges 6 at the gunwale edges 4 so as to fold alternately inwardlyand outwardly.

A folding bulkhead plate 7 of equilateral triangular form is connectedtransversely between the bulkhead edges 4 at each end of each inwardlyfolding pair of hull plates 1 by inner hinges 8, the bulkhead plate 7being divided at its centre line 9 into two symmetrical triangularportions 10 and 11 interconnected by outer hinges 12 so that theportions 10 and 11 will fold inwardly to lie between the hull plates 1when the pontoon is folded.

The relative sizes and the material densities of the hinges 5, 6, 8 and12 are selected to provide that the assembled plates are preferentiallyweighted at the keel edges 2 so that the hull plates will float uprightin the folded condition.

When the pontoon is open, the hull plates 1 and the bulkhead plates 7conjointly define six parallel hulls 13, all the interconnections ofwhich are internally sealed against ingress of water by a flexiblemembrane strip 14 adhesively applied to the conjoined members so as tobridge the gap between them.

The pontoon is bound in folded condition with a securing strap 30 (seeFIG. 3) and may be conveniently launched into a river from aconventional tilt truck 31.

Subsequent unfolding of the launched pontoon is illustrated in FIG. 4.The folded hulls 13 are first brought into alignment with the bank andthe nearest hull plate 1 is tethered to the bank. Two gunwale spacingbeams 40, each having seven spaced gunwale engagement sockets 41, arethen first engaged with the gunwale edge 3 of the outermost hull 13 andpushed outwardly from the bank so as to open the pontoon and permit thesockets 41 to engage successively with the gunwale edges 3 of each ofthe hulls 13.

A greater pontoon length may be provided by co-engaging the final socket41 with the outermost gunwale of a second folded pontoon insertedbetween the already unfolded one and the bank, which second pontoon isthen similarly unfolded with further spacing beams 40. It will beapparent that this process can be continued with successive pontoons andspacing beams to provide a ribbon bridge of desired length.

The spacing beams also serve as trackways across the pontoons or may beprovided with support means (not shown) for subsidiary trackways.

A typical pontoon having 22 hulls comprised by 44 hull plates eachmeasuring 9 m (at the gunwale edge)×2 m can be compacted fortransportation into a block which is no more than 2.4 m thick, andunfolded into a raft measuring 9 m×40 m having a depth of 1.8 m in a fewminutes without the use of cranes. The unladen pontoon, which has afree-board of 0.8 m, will survive a 9 knot current in the direction ofthe keels and can be crossed in currents of up to 6 knots by normalbridge loads typically reducing the free-board to 0.5 m.

When the pontoon is intended for use as a ferry, i.e. to be driven inthe direction of the keels, an apron (not shown) is preferably fittedover the bow and stern bulkheads so as to shed water from a centralridge to the outer-most gunwale to prevent swamping.

A particular advantage of the triangular multi-hull configuration ofthis embodiment of the invention over conventional flat-bottomedpontoons is the increased resistance offered by the folded platestructure to vertical crushing loads such as can be applied to a pontoonwhen it is in a grounded state.

A further advantage offered by the inherent stability of the foldedpontoon is the capability of deployment by dropping from a transportaircraft.

It will be seen that the equilateral triangular hull sections of theparticular embodiment described provide a pontoon which floats withapproximately one half of its depth submerged when not loaded. Otherembodiments of the present invention having less draught can be providedby including pairs of hull plates of shorter gunwale height in thesequence. For example, a pair of short gunwale-height plates so as toprovide consecutive pairs of hulls with intersecting V-sections, i.e.pairs mutually having an open W-section. In such an arrangement theconjoining bulkhead members would be extended to full gunwale height andthe gunwale spacing bars would engage with the full-height gunwalesonly. Obviously the number of pairs of short plates intermediate eachpair of full plates can be increased to reduce draught still further,but resistance of the structure to crushing loads will of coursedecrease proportionally.

INDUSTRIAL APPLICABILITY

The invention may be used to provide self-contained bridge supportingpontoons or ferrying pontoons as already described. Structures inaccordance with the invention may also be attached as folding sidepanels to an amphibious vehicle so as to be extendable when the vehicleis afloat, thereby to increase the vehicle's beam and buoyancy, andhence increase its stability and load bearing capacity.

I claim:
 1. A transportable pontoon comprising:a plurality of substantially planar hull members each having a (1) keel edge, (2) a gunwale edge, substantially parallel to said keel edge, and (3) at least two bulkhead edges; hinging means for hinging said members in sealed relationship at alternately conjoined keel edges and gunwale edges so as to fold in concertina fashion, thus allowing said pontoon to be substantially uniplanar when folded; and bulkhead member means extending in sealed relationship between each inwardly folding pair of hull members, for defining with said hull members a sequence of open top, hollow parallel hulls each having a triangular cross-section when said pontoon is extended.
 2. A pontoon as claimed in claim 1 characterised in that said each hull member is of a buoyant material and weighted at said keel edge so as to float substantially vertically when said pontoon is folded.
 3. A pontoon as claimed in claim 2 further including at least one gunwale spacing beam having spaced engagement means for engaging with said gunwale edges and holding said gunwale edges in spaced relation to one another.
 4. A pontoon as in claim 1 wherein said hinging means comprises:hinge means for folding said hull members in concertina fashion when said pontoon is extended; and sealing means, covering said hinge means, for ensuring that said hinging means forms a watertight seal between said hull members.
 5. A pontoon as in claim 4 wherein the relative sizes and weights of said hinge means are selected so as to weight said keel edge so that said pontoon will float upright in the folded position.
 6. A pontoon as in claim 4 wherein said sealing means is a flexible membrane strip.
 7. A method of launching a transportable pontoon having a plurality of planar hull members, hinge means for folding said hull members in a concertina fashion, and bulkhead members extending between inwardly folding hull members to form a series of parallel hulls with triangular cross-sections, comprising the steps of:a. dropping the folded pontoon into a water gap, b. tethering the near-end hull member of said folded pontoon to the bank of said water gap, c. engaging the far-end gunwale edge with a far-end engagement means of a gunwale spacing beam, and d. thrusting said far-end gunwale edge away from said bank with said gunwale spacing beam, whilst successively co-engaging each of said engagement means and gunwale edges in inwardly directed sequence as said pontoon extends.
 8. A transportable pontoon assembly, said pontoon being substantially flat when folded and being hollow, and open topped, and having a triangular cross-section when extended, comprising:a plurality of planar hull member means for forming a uniplanar structure when folded, and forming a generally triangular cross-section structure when extended, each said hull member having (1) a keel edge, adapted to be pointed downward when said pontoon is extended, (2) a gunwale edge, substantially parallel to said keel edge, and (3) at least two bulkhead edges; hinge means for pivotally attaching said hull members to one another so that said assembly can be folded: (1) to a substantially uniplanar structure and (2) in concertina fashion to a structure with a substantially triangular cross-section; sealing means, covering said hinge means, for ensuring a watertight seal between said hull member means; a plurality of bulkhead member means joined to said hull members along said bulkhead edges, for forming a uniplanar structure along with said hull member means when folded, and for extending in a generally perpendicular relation to said hull member means when said assembly is extended, and closing the ends of said triangular cross-section structure; bulkhead hinge means for pivotally attaching each of said bulkhead member means to a planar hull member along said bulkhead edge, so that said assembly can be folded: (1) to a uniplanar structure and (2) so that said bulkhead member means extend generally perpendicular to said hull member means; bulkhead sealing means, covering said bulkhead hinge means, for ensuring a watertight seal between said hull member means and said bulkhead member means along said bulkhead edge; and gunwale spacing beam means for holding said gunwale edges in spaced parallel relation when said assembly is extended.
 9. An assembly as in claim 8 wherein said gunwale spacing beam means includes means for consecutively engaging said gunwale spacing beam means with each said gunwale edge and thus extending said assembly. 